Through-silicon IR image to CAD database alignment

We perform automated alignment of a device´s CAD layout to its through silicon-IR image. Light refraction of the optical system blurs and distorts the shape and size of features, causing both edge-based and intensity-based cross-correlation techniques to fail. Our alignment methodology consists of pre-processing (equalization) of the images, followed by sub-resolution offset computation We apply a modeled point spread function (PSF) of the optical system to the CAD image to increase its resemblance to the optical image (resolution-equalization). Using our alignment algorithm, which combines image equalization, over-sampling, and cross-correlation, we demonstrate through-Silicon placement accuracy of 0.1 μ with a 1 μ resolution optical system.